The phenomenon of the armature magnetic reaction is known to persons skilled in the art. The armature magnetic reaction occurs when a current is circulating in the armature of the rotary electrical machine.
Taking as an example an alternator for a motor vehicle in which the armature is the stator of the machine, and the inductor is its rotor, the armature magnetic reaction occurs when the alternator is live and is discharging a current. The stator coils in which a current is circulating then produce a so-called armature reaction magnetic field, which can give rise to saturation and downgrade the magnetic field of the inductor. Subsequently, the electromagnetic force emf) is distorted (with possible saturation), and the performance of the alternator, in particular in terms of output, is adversely affected. This distortion of the emf produces harmonics which give rise to an increase in the Joule losses and iron losses of the machine. In addition, the performance relating to the acoustic vibrations and electromagnetic compatibility can also be affected by the inductor reaction.
In the field of rotary electrical machines with a high power level, it is known in the prior art to provide so-called armature reaction compensation auxiliary coils. These coils, which are included in the stator of the machine, produce a compensation magnetic field which opposes the armature reaction magnetic field, such as to reduce the effects.
The above-described solution can provide satisfactory compensation for the armature magnetic reaction in a rotary electrical machine, but it is unsuitable for the motor vehicle field, in which the constraints of weight, compactness and cost are extremely strict.
It is therefore desirable to propose a solution for compensation for armature magnetic reaction which is designed for the rotary electrical machines which are used in motor vehicles.